Component support and radioisotope generator including one or more component supports

ABSTRACT

The invention relates to a component support ( 29 ) for use in a radioisotope generator, the component support comprising a latching member ( 5 ) movable between an engaging position and an open position characterised by further including a bracing member ( 13 ) mechanically associated with the latching member and adapted to prevent movement of the latching member to the open position.

The present invention relates to an interengaging component supportwhich is particularly, but not exclusively, suited to implementation ina radioisotope generator of the type commonly used to generateradioisotopes such as technetium-99m (^(99m)Tc).

The diagnosis and/or treatment of disease in nuclear medicine constituteone of the major applications of short-lived radioisotopes. It isestimated that in nuclear medicine over 90% of diagnostic proceduresperformed worldwide annually use ^(99m)Tc labelledradio-pharmaceuticals. Given the short half-life of diagnosticradio-pharmaceuticals, it is helpful to have the facility to generatesuitable radioisotopes on site. Accordingly, the adoption of portablehospital/clinic size ^(99m)Tc generators has greatly increased over theyears. Portable radioisotope generators are used to obtain ashorter-lived daughter radioisotope which is the product of radioactivedecay of a longer-lived parent radioisotope, usually adsorbed on a bedin an ion exchange column. Conventionally, the radioisotope generatorincludes shielding around the ion exchange column containing the parentradioisotope along with means for eluting the daughter radioisotope fromthe column with an eluate, such as saline solution. In use, the eluateis passed through the ion exchange column and the daughter radioisotopeis collected in solution with the eluate, to be used as required.

In the case of ^(99m)Tc, this radioisotope is the principle product ofthe radioactive decay of ⁹⁹Mo. Within the generator, conventionally the99Mo is adsorbed on a bed of aluminium oxide and decays to generate^(99m)Tc. As the ^(99m)Tc has a relatively short half-life itestablishes a transient equilibrium within the ion exchange column afterapproximately twenty-four hours. Accordingly, the ^(99m)Tc can be eluteddaily from the ion exchange column by flushing a solution of chlorideions, i.e. sterile saline solution through the ion exchange column. Thisprompts an ion exchange reaction, in which the chloride ions displace^(99m)Tc but not 99Mo.

In the case of radio-pharmaceuticals, it is highly desirable for theradioisotope generation process to be performed under aseptic conditionsi.e. there should be no ingress of bacteria into the generator.Moreover, due to the fact that the isotopes used and generated with thegenerator are radioactive, and are thereby extremely hazardous if nothandled in the correct manner, the radioisotope generation process alsoshould be conducted under radiologically safe conditions. Naturally, itis desirable to ensure that when the elution process is performed, theradiological safety of the generator is not compromised. In particular,when the eluate is introduced into the generator, it is important forthe radiological safety of the generator to be maintained.

In trying to ensure adequate radiological protection, some knownradioisotope generators have tended to be of a complicated constructionincorporating a large number of components. However, the radiologicalprotection afforded by such structures can be compromised where theinterconnection of the various components is unreliable. Such complexstructures also add to the cost of the generator. It is thus importantthat the actual construction of the generator is reliable and allcomponent interconnections are secured to a high degree of certainty.

U.S. Pat. No. 3,946,238 describes a shielded radioisotope generatorcomprising a cylindrical shielded housing for a central repository. Therepository is bound by a removable top cover and side walls and a basewhich are made from lead and which act as the shielding. Within therepository a bottle is located which contains an ion exchange column inwhich ⁹⁹Mo is absorbed. When it is desired to add saline solution to thesystem to prompt the elution of ^(99m)Tc, the top cover is removed, andthe saline is introduced by way of a transfer pipette. The salinesolution is introduced by means of the pipette to an annular regionbetween the bottle and the inner surfaces of the shielding. From thisannular region the saline solution flows in a controlled manner into thebottle containing the ion exchange bed via a series of radial openingsin the wall of the bottle. The transfer pipette has a long handledesigned such that a user's hands always remain outside the generatorwhen saline is introduced into the annular region about the bottle. Itis apparent, however, that the removal of the top cover for the purposesof introducing the saline solution constitutes an unacceptableradiological risk as the interior of the repository is radioactive.

U.S. Pat. No. 3,564,256 describes a radioisotope generator havingquick-coupling members for the elution process. The generator includes acylindrical holder containing a radioactive substance bound to an ionexchange bed. The holder is closed by rubber plugs at both ends, and issurrounded by shielding having passages opposite each of the rubberplugs in which respective needles are located. At the outermost ends ofthe needles quick-coupling members are provided to enable a syringevessel containing a saline solution to be quickly and easily connectedto one of the needles and to enable a collection vessel to be connectedto the other of the two needles. In use, each one of the rubber plugs ofthe cylindrical holder is pierced by one of the needles to prompt theelution of ^(99m)Tc from the ion exchange column. Suitablequick-coupling members proposed in the document are conventionaldetachable injection needle to injection syringe connections.

U.S. Pat. No. 4,387,303 describes a radioisotope generator comprising acolumn having an elute inlet aperture and an elute outlet aperture andcontaining an ion exchange bed with the parent radioisotope. Both theelute inlet and outlet are in communication with channels in thesurrounding shielding. One of the channels, that is in communicationwith the elute outlet, is connected to a tapping point on the generatorvia an eluate conduit. The tapping point is adapted to receive anevacuated elution vial for collection of the daughter radioisotope insolution and consists of a hollow needle that pierces the seal to theevacuated elution vial. The eluate conduit is also in communication witha source of sterile air and the generator includes a device forinterrupting the elution process before the elution vial is filled byinterrupting the flow of sterile air. No information is provided withregard to the construction of the generator and in particular noinformation is provided as to how the hollow needle at the tapping pointis held in position.

The present invention seeks to provide a component support that issimple in construction but provides greater reliability than existingsimple component supports and so is particularly suited for use inradioisotope generators where there exists a need for a radioisotopegenerator that is simple in construction but which ensures the necessarydegree of sterility and radiological protection.

According to a first aspect of the present invention, there is provideda component support for use in a radioisotope generator, the componentsupport comprising a latching member movable between an engagingposition and an open position characterised by further including abracing member mechanically associated with the latching member andadapted to prevent movement of the latching member to the open position.

In a preferred embodiment of the present invention, the componentsupport may include a first plate on which the latching member ismounted, with the first plate including an opening at or adjacent thelatching member for receiving the bracing member. The opening in thefirst plate is preferably an aperture in the first plate adjacent thelatching member on the side of the latching member facing the directionof movement of the latching member from the engaging position to theopen position.

Preferably, the opening is of non-circular cross-section and the bracingmember has a corresponding non-circular cross-section. Also, thelatching member may additionally include a camming surface engageable bythe bracing member for urging the latching member away from the openposition.

More preferably the component support may also include a second plate onwhich the bracing member is mounted, the second plate being arranged tolie substantially parallel to the first plate when the bracing member isinserted through the opening in the first plate.

The latching member is preferably a generally L-shaped structureconsisting of a wall and a flange projecting therefrom, and in apreferred embodiment the latching member also includes a second flangearranged substantially parallel to the first flange for defining a slottherebetween. It is envisaged but by no means essential that thecomponent support comprises at least two opposing latching members andrespective bracing members.

According to a second aspect of the present invention there is provideda radioisotope generator having one or more component supports aspreviously described. The latching member of the generator may bemounted on a closure plate of the generator which include an opening forreceiving the bracing member, and wherein the bracing member is mountedon a cover plate of the generator such that insertion of the bracingmember into the opening mounts the cover plate over the closure plate.

Preferably, the radioisotope generator has two latching members mountedon the closure plate either side of a central component aperture andwherein the cover plate also includes a component aperture for alignmentwith the component aperture in the closure plate. The radioisotopegenerator may also include a fluid port comprising a hollow generallycylindrical body and a retaining plate, the hollow body being receivedin the component apertures in the closure plate and the cover plate andthe retaining plate being engaged by the opposed latching members forsecurely holding the fluid port in position.

In the preferred embodiment, the radioisotope generator includes acontainer consisting of a wall and a floor, with the opening to thecontainer being closed by a closure plate. With this arrangement thelatching member is located on the container wall and the closure plateincludes a bracket for engagement with the latching member and anopening at or adjacent the bracket and the bracing member is provided ona cover plate such that insertion of the bracing member into the openingin the closure plate aligns the bracing member with the latching memberthereby to prevent movement of the latching member to the open position.

An embodiment of the present invention will now be described, by way ofexample only, with reference to the accompanying figures, in which:

FIG. 1 illustrates a component support in accordance with the presentinvention; and

FIG. 2 illustrates a radioisotope generator incorporating supports fortapping spikes in accordance with the present invention.

The component support is Illustrated generally by reference numeral 29,and the component illustrated in FIG. 1 is a spike 1 which projectsthrough an aperture 2 in a plate 3 and has a planar mounting member 4that is held in position by a pair of latching members 5. The latchingmembers are movable between an engaging position in which they engagethe planar mounting member and an open position in which the planarmounting member is not restrained by the latching members. Each of thepair of latching members 5 includes a wall 6 projecting outwardly fromthe surface of the plate 3 (downwardly as illustrated in FIGS. 1 and 2).The walls 6 are each spaced from the aperture 2 diametrically oppositeone another across the aperture 2. A flange 7 is provided at the freeend of each wall 6. The flanges 7 on each of the walls project away fromthe walls towards one another and extend substantially parallel to theplate 3. A second flange 8, substantially parallel to the first flange7, is provided between the first flange 7 and the plate 3. The first 7and second 8 flanges thus form a slot 9 suitable for receiving a planarmember 4.

The plate 3 is preferably made from a hard plastics material and thewalls 6 and flanges 7, 8 are preferably moulded as a single unit withthe plate 3. This results in the walls 6 and flanges 7, 8 having a smalldegree of resiliency sufficient to be suitable for “snap-fit” engagementof a planar member within the slot 9 defined by the first 7 and second 8flanges. For this reason, as illustrated in FIG. 1, the first flange 7has a camming surface 10 facing away from the plate 3 for guiding andcentering a planar member 4 towards the slot 9 and for urging the smallamount of flexure of the opposed walls 6 necessary to permit the planarmember 4 to pass the periphery of the first flange 7 whereupon the walls6 ‘snap’ back into position with the planar member 4 located and held inthe slot 9 between the first and second flanges 7, 8.

Such a snap-fit connection is generally well-known and provides aparticularly quick method for securing two elements (in this case theplanar member 4 and the plate 3) together. However, the fact that thismanner of securement demands a small degree of flexure of the walls 6,generally renders such a means of securement undesirable incircumstances where the securement must be highly reliable. An externalforce applied to the plate 3 is capable of causing flexure of the walls6 to the extent that the planar member 4 is accidentally freed from theslot 9. For this reason, snap-fit connections have not been consideredsuitable in the construction of radioisotope generators.

The component supports 29 illustrated in FIGS. 1 and 2 however provide agreatly improved reliability of securement over convention snap-fitconnectors, which renders the component supports 29 particularly suitedfor use in radioisotope generators. The component supports 29 include acover 11 that is arranged to overlie the plate 3. The cover 11 has acomponent aperture 12 for alignment with the aperture 2 in the plate 3.The cover 11 also has a pair of bracing members 13 that project(downwardly in FIGS. 1 and 2) away from the cover 11. Also, adjacenteach of the walls 6, on the opposite side of each of the walls 6 to theflanges 7, 8, respective brace apertures 14 are provided in the plate 3.The bracing members 13 on the cover 11 are positioned either side of thecomponent aperture 12 so as to be aligned with the brace apertures 14 inthe plate 3. The brace apertures 14 are sized to permit the passage ofthe bracing members 13 and preferably are non-circular in cross-sectionso that the bracing member 13 is keyed into the brace aperture 14. Withthe cover 11 positioned over the plate 3 and the bracing members 13inserted into the brace apertures 14, the bracing members 13 aremechanically associated with the walls 6, and act as braces to the walls6. This substantially prevents outward flexure of the walls 6. In thisway, the reliability of the component support 29 is greatly enhanced.

In a particularly preferred embodiment, each associated wall 6 andbracing member 13 have co-operable camming surfaces and followers. InFIG. 1 the camming surface 15 is on the wall 6 facing towards thebracing member 13. This enables the bracing member 13 to actively engagewith and urge the wall 6 inwardly towards the planar member 4 wheninserted in the slot 9 defined by the first and second flanges 7, 8.This further improves the reliability of the securement of the componentprovided by the component supports 29.

FIG. 2 illustrates an implementation of the component supports in aradioisotope generator 16. The radioisotope generator 16 has an outercontainer 17, a closure plate, referred to herein as a top plate 3 whichis sealingly secured to the outer container 17, and a separate top cover11 which is secured to the outer container 17 over the top plate 3.Inside the outer container 17 a radioactive shield 18 is located whichis preferably, but not exclusively, made from either lead or a depleteduranium core within a stainless steel shell. The radioactive shield 18surrounds a tube 19 containing an ion exchange column 20. The ionexchange column 20 preferably consists of a mixture of aluminium andsilica, onto which molybdenum in the form of its radioactive isotope,⁹⁹Mo is adsorbed. The tube 19 containing the ion exchange column 20 hasfrangible rubber seals 21 and 22 at opposing ends 23 and 24 which, asillustrated, when in use are pierced by respective hollow needles 25 and26.

Each of the hollow needles 25 and 26 are in fluid communication withrespective fluid conduits 27, 28 which in turn are in respective fluidcommunication with an eluent inlet and an eluate outlet. The fluidconduits 27, 28 are preferably flexible plastics tubing and in the caseof the tubing 27 that communicates with the hollow needle 25 at the top23 of the ion exchange column 20, the length of the tubing 27 is muchgreater than the minimum required to connect the hollow needle 25 withthe eluent inlet.

The top plate 3 of the radioisotope generator 16 has a pair of apertures2 through which the respective eluent inlet and eluate outlet componentsproject. The eluent inlet and eluate outlet components are each hollowspikes 1 though in the case of the inlet component the hollow spikeadditionally includes a filtered air inlet 30. The hollow spike 1consists of an elongate generally cylindrical spike body 31 and anannular retaining plate 32 which is attached to or is moulded as asingle part with one end of the spike body 31. The opposing end of thespike body 31 is shaped to a point and has an aperture 33 communicatingwith the interior of the spike body 31 adjacent the point. This pointedend of the spike body 31 is shaped so that it is capable of piercing asealing membrane of the type commonly found with sample vials. Theannular retaining plate 32 forms a skirt projecting outwardly from thespike body 31 and may be continuous around the spike body 31 ordiscontinuous in the form of a plurality of discrete projections.

The top cover 11 of the radioisotope generator 16 also includes a pairof apertures 12 arranged so as to align with the apertures 2 in the topplate 3 and shaped to allow through passage of the spike body 31. Thus,each of the hollow spikes 1 is arranged to be held and supported by itsannular retaining plate 32 by latching members 5 located on the insideof the top plate 3 whilst the hollow spike body 31 projects through theapertures in both the top plate 3 and the top cover 11 to the exteriorof the outer container 17. Each one of the apertures 12 in the top cover11 is located at the bottom of a well 34 that is shaped to receive andsupport either an isotope collection vial 35 or a saline supply vial 36.Thus, both vials 35, 36 are housed outside of the outer container 17 andare not exposed to radiation from the ion exchange column 20.

The hollow spikes 1 are held in place by the component supports 29 asdescribed earlier with reference to FIG. 1. Thus, the spike body 31projects through the aligned apertures in the top plate 3 and the topcover 11 and is securely held in position by engagement of the annularretaining plate 32 in the slot 9 defined by the first and second flanges7, 8 of the latching members 5. Retention of the plate 32 in the slot 9is maintained by the supporting action of the bracing members 13 outsideof the walls 6 of the latching members 5 which substantially preventoutward flexure of the walls 6.

When the radioisotope generator 16 is constructed, the spike body 31 isinserted through the aperture 2 in the top plate 3 and the annularretaining plate 32 contacts the camming surfaces 10 on an opposing pairof first flanges 7. Further pressure applied to the retaining plate 32forces outward flexure of the walls 6 supporting the first flanges 7until the retaining plate 32 is able to pass the free end of the firstflanges 7. Once the retaining plate 32 has passed the first flanges 7the external pressure on the walls 6 is eased and the walls 6 ‘snap’back to their normal position locating the retaining plate 32 in theslots 9 defined by the first and second flanges 7 and 8. The top cover11 is then positioned over the top plate 3 with the apertures 12 in thetop cover 11 aligned with the spike body 31 and the bracing members 13aligned with apertures 2 in the top plate 3 adjacent each of the walls6. As the top cover 11 is brought into contact with the top plate 3 thebracing members 13 pass through the apertures 2 in the top plate 3 so asto be positioned next to, and preferably in contact with, the outersurfaces of the walls 6. The interaction of the bracing members 13 onthe top cover 11 and the walls 6 of the top plate 3 thus providereliable securement of the retaining plate 32 of the hollow spike 1 inthe slot 9 defined by the first and second flanges 7, 8. The tubing 27and 28 is then fluidly attached to the hollow spikes 1 and the outercontainer 17 is closed when the top plate 3 and the top cover 11 aresecured to the container.

When it is desired to attach a vial 35 or 36 to the hollow spike 1, auser positions the frangible seal of the vial over the pointed end ofthe spike and pushes the vial down onto the spike 1. This causes theseal on the vial 35 or 36 to be pierced establishing fluid communicationbetween the spike 1 and the vial. Once the seal has been pieced by thespike 1, the vial is pushed down over the spike 1 until it rests and issupported by the well 34 in the top cover 11.

In order to supply the ion exchange column 20 with the chloride ionsrequired for elution of the radioisotope, saline solution 37 is drawnthrough the ion exchange column 20, by establishing a pressuredifferential across the ion exchange column 20. This is accomplished byconnecting the saline supply vial 36 to the eluent inlet which is influid communication with the top end 23 of the ion exchange column 20via the tubing 27 and hollow needle 25 and connecting an evacuatedcollection vial 35 to the eluate outlet which is in fluid communicationwith the bottom end 24 of the ion exchange column 20 via the tubing 28and hollow needle 26. The pressure differential is established by virtueof the fluid pressure of the saline in the supply vial 36 and theextremely low pressure in the evacuated collection vial 35. This urgespassage of the saline solution 37 through the ion exchange column 20 tothe collection vial 35 carrying with it the daughter radioisotope.

The component support is simple in design but by the interaction of thebracing member on one plate with the wall of the snap-fit component onthe other plate and highly reliable component support is provided.Although reference has been made in the description to a componentsupport suitable for a hollow spike, it will be apparent that thecomponent support of the present invention may be employed withalternative components that are intended to be secured in a snap-fitholder.

For example, the component support may be used as a means for attachingthe top plate to the outer container of the radioisotope generator. Withthis arrangement, latching members are attached to the inner side wallsof the outer container. Each latching member is spaced from the wall ofthe outer container by means of a bridge element so as to define abracket receiving region between the latching member and the wall of thecontainer. Thus, the wall of the latching member is arrangedsubstantially parallel to the container wall and the slot defined by thepaired flanges mounted on the wall of the latching member liessubstantially perpendicular to the container wall. This arrangement alsorequires the top plate to have an equivalent number of brackets forlocation and engagement with respective latching members. Thus, as thetop plate is lowered into position, the bracket attached to theperiphery of the top plate and projecting downwardly therefrom, engagesthe first of the flanges on the latching member. The bracket urges thelatching member to flex away from the container wall thereby enlargingthe bracket receiving region until the bracket is capable of passing theperiphery of the flange whereupon the latching member snaps back intoposition trapping part of the bracket in the slot defined by the twoflanges. As described previously, the bracing member projects from thetop cover and is locatable in an aperture in the top plate, such that,as before, it is mechanically associated with the latching member andacts to brace the latching member against flexure.

It is not a requirement of the present invention that the bracing meansis locatable through an aperture in the top plate such that it acts asan exterior abutment to the component support wall. For example, it isalternatively envisaged that the component support wall may include ablind bore, into which the bracing means is inserted, to provide thedesired improved support for the latching member.

Moreover, it is not a requirement of the present invention that theplates of the component support contain apertures through which thecomponent passes. Instead, the component may extend away from thesurface of the first plate bearing the walls of the component support(in the illustrated embodiment the top plate 3) in which case the secondplate (in the illustrated embodiment the top cover 11) need only alignthe bracing members with the brace apertures in the first plate.Furthermore, although paired flanges defining a slot are illustratedabove, it will be appreciated that the slot may be defined between asingle flange and the surface of the first plate. Further andalternative features of the component support are envisaged withoutdeparting from the scope of the present invention as claimed.

1. A component support for use in a radioisotope generator, thecomponent support comprising a latching member movable between anengaging position and an open position characterised by furtherincluding a bracing member mechanically associated with the latchingmember and adapted to prevent movement of the latching member to theopen position.
 2. A component support as claimed in claim 1, furtherincluding a first plate on which said latching member is mounted, saidfirst plate including an opening at or adjacent the latching member forreceiving the bracing member.
 3. A component support as claimed in claim2, wherein said opening in said first plate is an aperture in said firstplate adjacent the latching member on the side of the latching memberfacing the direction of movement of the latching member from saidengaging position to said open position.
 4. A component support asclaimed in claim 1, wherein said opening is of non-circularcross-section and said bracing member has a corresponding non-circularcross-section.
 5. A component support as claimed in claim 1, whereinsaid latching member includes a camming surface engageable by saidbracing member for urging said latching member away from said openposition.
 6. A component support as claimed in claim 1, furtherincluding a second plate on which said bracing member is mounted, saidsecond plate being arranged to lie substantially parallel to said firstplate when said bracing member is inserted through said opening in saidfirst plate.
 7. A component support as claimed in claim 1, wherein saidlatching member comprises a generally L-shaped structure consisting of awall and a flange projecting therefrom.
 8. A component support asclaimed in claim 7, further including a second flange arrangedsubstantially parallel to said first flange for defining a slottherebetween.
 9. A component support as claimed in claim 1, comprisingat least two opposing latching members and respective bracing members.10. A radioisotope generator including one or more component supports asclaimed in claim
 1. 11. A radioisotope generator as claimed in claim 10,wherein said latching member is mounted on a closure plate of thegenerator and includes an opening for receiving said bracing member, andwherein said bracing member is mounted on a cover plate of saidgenerator such that insertion of said bracing member into said openingmounts said cover plate over said closure plate.
 12. A radioisotopegenerator as claimed in 11, having two latching members mounted on saidclosure plate either side of a central component aperture and whereinsaid cover plate also includes a component aperture for alignment withthe component aperture in said closure plate.
 13. A radioisotopegenerator as claimed in 12, further including a fluid port comprising ahollow generally cylindrical body and a retaining plate, said hollowbody being received in the component apertures in said closer plate andsaid cover plate and said retaining plate being engaged by said opposedlatching members for securely holding said fluid port in position.
 14. Aradioisotope generator as claimed in claim 10, further including acontainer consisting of a wall and a floor and with the opening to thecontainer being closed by a closure plate, said latching member beinglocated on said container wall and wherein said closure plate includes abracket for engagement with said latching member and an opening at oradjacent said bracket and said bracing member is provided on a coverplate such that insertion of the bracing member into said opening insaid closure plate aligns said bracing member with said latching memberthereby to prevent movement of the latching member to said openposition.